I am conducting the following design and I wanted to know if my initial hypothesis/assumptions were correct.

I am conducting a within-subject design. Each patient will receive six treatments on their skin, then 24 hours later I will check their skin and measure the result. I would like to compare the six treatments within subject. The values are either "100, 200, 300, 400, 500 or 600" for each treatment. I only test each individual once. I have as hypothesis that four of the treatments should be the exact same, while the two other ones should be the same. Any idea what statistical test I should be using in the future and as far as sample size, anyone have any thoughts?